RCA Victor RCA-6T71 (Where to start?"
 

Hello everyone. I'm back after a long interlude about 4 years.
But I've got a new TV and this will be the first TV I've actually repaired that is this old, And I was wondering where to start? I've replaced the vertical output tube because it was missing and cleaned the dust out and checked for shorts but I don't know where to go from here? after starting it on the light bulb cord no shorts I plugged it into mains and god buzz and some soft audio under the HUM and a raster. So any ideas on where to start with gitting this thing ready for everyday use again? :scratch2:

Heres a picture of what I got so far,
http://i1118.photobucket.com/albums/...ps5ddaa4f2.jpg

http://i1118.photobucket.com/albums/...ps28efb470.jpg

Hi Coshi, welcome back!

All the basics on this set. At very least, replace all of the electrolytic capacitors. Replace all of the bypass capacitors second. I recommend replacing all capacitors if indeed you want to use this set as a 'daily driver!'

These RCAs will also need some peaking coils replaced. The two types they used in these prone to fail look like a blob of white wax with leads coming out either end, or a blob of reddish or brown ceramic, also with leads coming out either end. Some are just coils, and some are coils wrapped around resistors. Easy to replicate with the help of a schematic. There are about 5 or 6. Mica caps coupling the IF stages together should also be replaced, but not absolutely necessary unless they prove to have problems... so check those last.

Raster on the screen is a great start!

From the shrunken raster it's clear your B+ voltage is way low. First step is to replace all the Electrolytic Capacitors, that might improve things a lot but ultimately all the paper capacitors will have to be replaced for it to work correctly.

It's a good start that you at least have some raster, that indicates that all the essential parts are working at this point, CRT, Flyback, Yoke, deflection circuits.

If you change all the capacitors it will likely start working fairly well though there are often other minor issues like drifted resistors and dirty controls and such.

That is what I was thinking. everything seams to be about 70% all the major parts are working. What I was wondering is where do I get the electrolytic condensers? I found the modern replacement for the paper condensers. But the electrolytics are strange values. Plus how do you replace those big metal cans?

This article has a lot of information about replacing capacitors, including various methods of replacing those in cans:

http://antiqueradio.org/recap.htm

This article may also be helpful:

http://antiqueradio.org/FirstStepsInRestoration.htm

Regards,

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Hello again,
Thanks everyone so far I've ordered the paper caps but not the electrolytic filter caps. (There too expensive right now.) I was wondering if I could feed the set 110v DC untell I can replace the filter caps. Or would this damage something?

Absolutely NOT!
It's strictly an AC, transformer powered chassis.
No choice, but to replace the electrolytic caps. :sigh:

Thanks for getting back to me so fast. Right on I'll replace the electrolytic condensers then. (I'm NOT going to try the DC thing. since its dangerous) But could you tell me why its bad?

Transformers are straight AC devices. Sixty polarity alternations a second.
Google AC power. There's a good explanation there. :scratch2:

OK, Update time, I've got the picture tube cleaned safely put back into the Cabinet I put foam rubber insulating strips around the safety glass and to cushion the bottom of the picture tube.

But I found that the HV lead that connects to the edge of the picture tube isnt getting good connection to the edge of the screen. I have it taped to it with a peace of rubber tape, How SHOULD it be connected? I'll get a picture of it soon as I can.

http://i1118.photobucket.com/albums/...pse55e1344.jpg

http://i1118.photobucket.com/albums/...ps8ff8721f.jpg

Wonderful News! After cleaning the controls or I believe there called Potentiometer's, The picture is now filling almost the hole screen, Is this right? Should there be any change I have it hooked to a VCR and some sound is coming through but no video just a blank screen?

http://i1118.photobucket.com/albums/...ps41b0ab08.jpg

Speaking from the experience of being elbow deep in a couple of these KCS47 chassis, I actually shuddered when I saw the model number stamped into the back of your chassis :)

But, since your set is this far along, it obviously didn't have any of the horrible repair work that was done to some of these at different points in the 1950s.

Now, my advice is this. As tempting as it may be, don't run this set any more until it's gone through. These KCS47's were one of RCA's most unreliable black and white chassis of the era. The fact that it's producing a raster is evidence that it was either well cared for, or used very little.

At the very very least, the tubes have to be checked, and all capacitors need replacement. Though you're getting a raster, these sets were designed to operate with a pretty wide tolerance and still get a picture. You could have shorted or open components or tubes in the chassis, and if you run this set hoping it'll straighten out on its own, it won't, and something *will* smoke or burn out.

If you're not keen on tackling the job yourself, tell us where you're located....I'm sure one of us would be glad to give you a hand :)

Well I have never done work like this before. I would like to learn how to do the work. BUT in the end all I really want is to get this set back to everyday use.
Thanks mr/ms.Kamakiri I live in Southern Maryland is there a group around here?

It's Mr. ;) . My name is Tim.

I did a couple sets for people in the DC metro. I don't know what others charge for such a job, but I'd hook up with someone local to you.

While this set can be brought back to life and used, using it as a daily driver it is eventually going to need additional service no matter how it is restored. Tubes, filter chokes, transformers, etc failed when the sets were a lot newer than they are now. And plan to invest in a tube tester, failures among tubes are commonplace.

Putting a dozen or so hours a month on a KCS47 that's been restored isn't out of the question, but for long-term reliability you'd be better off with a different set if you plan to use it as TVs are used today. Just my .02....

I have a few round screen TV's - but not one exactly like yours.
Mine, the HV Anode lead typically clips to the metal CRT bell housing.
I assume that your CRT housing - the black colored part is metal.

DO NOT TOUCH that metal housing -- there is approximately 12K volts
on it. AND, when you remove power, you need TO DISCHARGE that voltage.
One way to discharge it is to take an insulated screw driver and a clip
lead with alligator clips on both ends of the clip lead. Connect one end
to the metal chassis and the other to the metal part of the screwdriver.
When you unplug your TV, then hold the insulated part of the screw driver
with the clip lead attached and touch the HV Anode wire. In essence you
are grounding out to the chassis the voltage on the capacitance in the circuit.
Do this a couple more times as the voltage sometimes builds back up.
I hate getting shocked :-)

Here are photos showing how the HV Anode wire connects in my Zenith
and Raytheon televisions:

One more tip, when you are moving your TV, keep this in mind what happened to me.
I was bench testing my Raytheon TV and got it working the way I wanted.
Always being careful, when I pull the power I immediately shorted out the Anode
lead on the CRT. Then I got the cabinet ready for the chassis and went back
to pick up the chassis to install in the cabinet. Something told me to ground that
Anode just to be sure and when I did I noted a spark. I had already shorted it out
once but the charge built back up. There is a name for this phenomenon - can't
recall right now. Imagine how pissed I would be if I had that big old chassis
in my hands, got shocked and dropped the chassis and CRT together.

Be careful and its going to be fun.

It's been ages, since I worked on one of those.
IIRC, the anode lead is clipped or connected to one of the spring contacts, located around the front of the CRT.
They also used to use a foam gasket, that crumbled after a while, to keep the dust out, between the CRT front and the safety glass.

Thats what I expect from a set this old. Mr.Tim I go to DC often would you be intrested in helping with this set? I could pay you.

As for using a different set what would you suggest? I was hoping to over time make the set more reliable by replacing broken parts with more robust parts.

I have a friend in your area of MD that comes this way quite often, and he's brought his sets (along with others) for me to work on when he comes up. So far I've worked on 6 sets for him. That's really not a job that can be done in a day. The fastest restoration that I've done took me 3 weeks from unknown to done and running.

As far as more robust parts, you can to a degree. Things like capacitors and resistors can be upgraded significantly from their original counterparts, making them much more reliable. Things like transformers, yokes, and other hard parts, you pretty much have to use what's available, which means whatever the set came with. Fortunately it looks like on your set, that all of that stuff is still good.

Now as far as a reliable "daily driver" set, you'll get a lot of opinions here, but IMO you just can't beat an early 1960s Zenith. They're the top of the list as far as reliability goes.

Here's a picture of my 1961 23" Zenith console. I use this set almost every day and have put hundreds of hours on it since restoring it with no issues. If you're looking for a set of a similar era to yours, just about any Admiral is an excellent choice.

I really didn't mean to temper your enthusiasm on the set you've got. It's a very nice looking set, and should be able to be made into a watchable set with little difficulty. But if long-term reliability is the goal of owning a vintage TV with little else to do other than turn it on and watch it, this may not be your ideal candidate.

That lead should go between one of the metal spring clips, and, the metal bell of the tube. This set uses a number of hv capacitors in the hv cage, and, underneath. Value, and, voltage are very important.
As said, the electrolytics are no good. I can see hum patterns on the screen telling me the electrolytics are shot.

This is a 117Volt, 60 cycle ac only set. If you try using it on dc you will destroy the power transformer.
The KCS 47's don't usually use the older white chokes that went bad. These chokes are more reliable.
This set works on very high dc voltages, and, I would highly recommend you get someone to help that knows what they are doing. And, yes, unfortunately, they are not a highly reliable set. I have one I've bben restoring, and, every time it acts like it's finished, something else goes wrong.
It's worth saving, but, it will need a lot of careful restoration.
Good luck.
Bill Cahilll

I see... Is this set worth anything? Would I be able to trade it for a less valued set? I'm looking for a black and white set from 1960 or earlier. I was told that a muntz set would be unreliable but easy to repair dew the few parts. And yes I've been working on this set for weeks I expect it to take a long time.

For what it's worth, I've parted out two RCA KCS-47 sets, one of which I had been trying to coax a respectable picture out of. Even when fully restored, they're mediocre performers at best. I think you would be much happier with a '48 or '49 Admiral. They make fantastic daily drivers. My Admiral 20X122 is easily the most reliable set in my collection, bar perhaps my RCA 630TS, and it's a very simplistic and straightforward set to work on. Just my 2 cents...

The problem is that even though your set shows signs of life, unless the prospective buyer has a desire for that particular set or is new to the hobby, there really aren't many sets that hold a lower value. I try to stay away from all RCA B&W products from 1951-1955 or so because I'm familiar with the pitfalls of them.

I'd peg that one at a solid $75 as it sits, to the right person. Typically, $50. My fully restored 1961 Zenith, though, is probably worth $150 at best, even though I probably have $75 into it in parts. We restore them for the challenge, the admiration and appreciation of the genius that it took to build them, and the fact that it's good cheap entertainment. Plus they're fun to watch. Kinda like Sea Monkeys, we sit in front of them just to see what they'll do :D

What's your bottom line budget on a set?

Well I payed 150 for this set... I was hoping to get a set that was easy to fix. What do you mean a bottom line budget? and ordered 17 dollars worth of caps.

Bottom line budget, as what you'd want to spend on another set if this one didn't pan out.

Funny, I have my Zenith listed on CL for $150 right now, figuring if I sold it, it'd be incentive for me to finish my DuMont RA-113. Got absolutely no bites on it.

http://buffalo.craigslist.org/atq/4484509506.html

OH! Would you be willing to trade? I have a tube tester and a oscilloscope and a bunch of old tube type stuff that is working. And of coarse this TV that I'm working on. And some money?

Back to work on this one. I have photographed the bottom and wire connections. 9So I can put it back) But what I'm now working on the filter cans. so the question is what values can be used in place of these for better reliability

MFD VOLTS
35 450
35 450
10 450
5 450

Replacing them with modern caps of the same values will give you better reliability because modern caps are greatly superior to those made 60 years ago. This article has lots of information about choosing replacement capacitors:

http://antiqueradio.org/recap.htm

I normally choose replacement caps with the same capacitance values and voltage ratings as the originals. There is no real advantage to using caps with a higher voltage rating than the originals. Higher-voltage caps will be larger and they will cost more, but otherwise your TV will perform the same either way.

Some folks make sure that new electrolytic caps have a good maximum temperature rating -- say, 105 C or higher.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

35s are no longer made, but 33 MFD is plenty close enough. Capacitor life is exponential with regard to temperature rating so 105C last considerably longer than 85C caps but they also cost more.

Ok, So I am very VERY dumb I fail to understand how to replace the electrolytic caps. I Have the 4 replacement caps for the metal can But how do I know where each one hooks to?

There are symbols next to each lug. Typically square, half-circle and triangle with the 4th lug having no symbol. Those will match up with the label on the can and possibly the schematic.

This recapping article has links to several articles with photos that illustrate different ways to replace electrolytics that are in cans:

http://antiqueradio.org/recap.htm

Some people just disconnect the old can connections and install the new electrolytics on a terminal strip that they fasten nearby. You can also cut off the old can and drill holes in the base and install the new cap leads through those holes (soldering them to the original terminals). Another way is to cut off the can, empty it, and "restuff" the can with your new electrolytics.

All of those methods are shown in the articles, along with photos and explanations of what is being done.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html